(Updates with comments from panelists, background)
By Toni Clarke
Aug 6 (Reuters) - Bayer AG’s experimental drug to treat two types of pulmonary hypertension should be approved at doses proposed by the company, an advisory panel to the U.S. Food and Drug Administration ruled on Tuesday.
The panel voted 11-0 that the FDA should approve the drug, riociguat, which in clinical trials extended the distance patients could walk during a six-minute test.
The FDA is not obliged to follow the recommendation of its advisory panel, but typically does so. If approved, the drug would be sold under the brand name Adempas.
The drug is designed to treat chronic thromboembolic pulmonary hypertension, a rare disease typically caused by blood clots that restrict the flow of blood from the heart to the lungs. The drug would be used for patients who are not candidates for surgery to remove the clots.
It is also designed to treat pulmonary arterial hypertension, in which arteries of the lungs constrict, forcing the heart to work harder. Symptoms of both conditions are similar and include shortness of breath, fatigue, weakness and potential heart failure.
If approved, the drug is expected to generate sales of $610 million, according to the average estimate of six analysts polled by Thomson Reuters.
Reviewers for the FDA recommended the drug be approved at doses lower than the maximum 2.5 milligram dose proposed by Bayer. They argued that a starting dose of 0.5 milligrams and maximum dose of 1.5 milligrams three times a day would confer the same benefit as the higher dose with a reduced risk of side effects, particularly hypotension, or low blood pressure.
Low blood pressure can cause dizziness, fainting, nausea and potentially loss of consciousness.
Dr. Preston Dunnmon of the FDA said the agency was concerned that most people with coronary artery disease were excluded from Bayer’s clinical trials and that in an unscreened population the negative impact from hypotension could be more prevalent than thought.
Dr. John Newman, professor of pulmonary medicine at Vanderbilt School of Medicine, agreed, saying that once the drug has been approved “we don’t really know what the increased risk will be in a general population.”
Overall, however, panelists recommended approving the drug with a 2.5 milligram limit, saying they wanted as many options as possible and that decisions on dosing should be left to physicians.
Dr. Stuart Rich, a panel member and professor of medicine at the University of Chicago Pritzker School of Medicine, said he was not concerned about low blood pressure unless it caused symptoms, and those numbers were relatively low in the trial.
Rich said he was impressed with the apparent ability of the higher dose of the drug to increase cardiac output, or the volume of blood pumped by the heart per minute. (Reporting by Toni Clarke in Washington; Editing by John Wallace, Gerald E. McCormick and Andrew Hay)